Throughout my time coaching with Rip and Stef, I've heard many different reasons as to why someone can't low bar back squat. We've had a few older trainees who took a few more warm up sets to hit the low bar position but rarely (none comes to mind but I won't say never) is it not done. This weekend, we had a very diverse group of body types; ages; and number of limbs to deal with.
And not one person was unable to hit a low bar squat position all morning. We had Bill who, at 6'6", has been one of our tallest attendees and Andy (I don't know how tall he is but he's a ways away from 6'6".) We had a very large (that's all I'm saying on that) John and a very not large Colin (that's all I'm saying on that.) All hit the low bar squat, at full depth just fine.
We've all heard many excuses as to why someone can't low bar and in many rare (heh) cases, these folks are right. But if we let our lifters tell us right off that bat that they're too big; or too small; or too tall; or too whatever so they can't put themselves in that position...well then we're not very good coaches are we? Are you?
Rip discusses at length why the LBBS is superior for general strength training (more muscle mass, longer range of motion, etc.) There is also extensive conversation on the Biomechanics of the LBBS and why they are not only safe, but necessary in avoiding injury. Dave Wood, one of our friends from the DFW area who at 57 has started squatting with this method remarked that this is the first time he's ever performed squats without knee and back pain. There ya go.